Nginx choosing wrong server

I want to handle to handle sub.domain.com and domain.com with different server blocks.
So I created the following config:

server {
  listen 443 ssl;

  server_name sub.domain.com;

  location / {
    ...
  }
}

server {
  listen 443 ssl;

  server_name domain.com;

  location / {
    ...
  }
}

Requests to sub.domain.com get correctly handled tby the first server block. However requests to domain.com also get handled by the first one.
Why?

From what I understand from the docs, requests to domain.com shouldn’t be matched by sub.domain.com?